1. Field of the Invention
The present invention relates to processing for rotating a chest image, and particularly to a chest image rotation apparatus and method that is suitable for rotating the chest image by using the direction of the vertebral bodies (corpus vertebrae) in the chest image. Further, the present invention relates to a computer-readable recording-medium stored therein a program for the apparatus and method.
2. Description of the Related Art
Conventionally, in the fields of medicine, a technique for automatically rotating a chest image that has been obtained by imaging the chest of a subject (patient) from the front side thereof is essential to observation of the subject by a user (doctor or the like) when the subject was imaged in inappropriate posture (position).
Meanwhile, a technique for displaying an image of a pair of breasts on a monitor in such a manner that the breasts, which have been imaged in the same direction, face each other has been proposed in Japanese Unexamined Patent Publication No. 2001-222704. In this technique, the breast image obtained by imaging is rotated based on information about the position of the subject.
Further, a method for extracting a feature value from a predetermined partial region of a chest image obtained by imaging a subject from the front side thereof has been proposed in Japanese Unexamined Patent Publication No. 2002-360551. In this method, a rotation angle is detected based on the predetermined partial region of the chest image and the direction of an end of a sensor, and the chest image is rotated based on the detection result. Further, the feature value is extracted from the partial region after rotation.
However, in actual medical scenes, a need for imaging a patient who cannot move from his/her bed in the patient's room of a hospital, a need for emergency imaging in an operating room of a hospital and the like are increasing in recent years. Therefore, a mobile X-ray apparatus (hereinafter, referred to as “mobile cart (mobile unit) M for doctor's visits to patients' rooms” (mobile cart M)) as illustrated in FIG. 9 will be used in actual medical scenes in the near future. The mobile cart M can be moved to the patient's room or the like to image the chest or the like of the patient. For example, when the mobile cart M is used to image the patient, a cassette 70 is placed on the back side of the subject (patient) who is lying on a bed 80, as illustrated in FIG. 10. Therefore, if the cassette 70 is set in an inappropriate manner, or if the posture of the patient is not appropriate, the patient, the axis of which is significantly inclined with respect to the sides of the cassette 70, is imaged in some cases.
In such cases, the method disclosed in Japanese Unexamined Patent Publication No. 2001-222704 is insufficient to solve the problem. In the method disclosed in Japanese Unexamined Patent Publication No. 2001-222704, it is impossible to rotate an image based on the degree of inclination of an anatomically characteristic region (for example, a lung field, a vertebral body, a breast or the like) in the image. Further, it is impossible to rotate the image without using the information about the position of the subject.
Further, in the method disclosed in Japanese Unexamined Patent Publication No. 2002-360551, when the subject, the axis of which is significantly inclined, has been imaged, if a feature value is extracted from a predetermined partial region of the image, the shape of the predetermined partial region differs according to the inclination angle. Therefore, it is impossible to extract an accurate feature value. Hence, it is impossible to accurate extract the predetermined partial region. Further, there is a problem that information about the inclination of an edge of a sensor is necessary to rotate the image, and that it is impossible to rotate the image by using only the information about the image.